Two instructors and a doctoral student of the Graduate Institute of Ferrous Technology at Pohang University of Science and Technology, South Korea, make up the team behind the discovery. Photo: Graduate Institute of Ferrous Technology/Wikimedia Commons

The report, “Spending Through the Roof,” says that apartment building owners pay an average of $3,400 a year to replace heat lost through the roof. In taller buildings, the cost can be more than $20,000 a year. Illustration: Urban Green Council